Fertilizer – The Proper Ratio

Q: According to the Atlanta Rose Society I should fertilize regularly with a “balanced” fertilizer like 10-10-10 or 16-4-8. Intuitively, the former is “balanced” with equal percentages (10-10-10), whereas the latter is not. Am I misunderstanding something?

A: Although semantically it seems that 10-10-10 is a “balanced” fertilizer, in truth it is unbalanced, because it contains much more phosphorus than plants need. Imagine if you were fed a pound of protein, a pound of carbohydrates and a pound of vitamins and minerals each day. You’d get a “balanced” diet but it would be wildly mis-proportioned for human health. In truth, most plants thrive with fertilizers that contain a 4-1-2 ratio of nitrogen, phosphorus and potassium. 16-4-8 is an example. This is a fertilizer ratio that’s balanced to most plants’ needs. Lawn fertilizers that contain a high percentage of nitrogen, such as 26-0-4, are balanced to the needs of grass, which demands more nitrogen than flowers or shrubs. I admit that I’m guilty of recommending 10-10-10. My excuse is that it is readily available at garden centers and 16-4-8 is not. If you’re looking for a general purpose fertilizer, try to find a product that semi-sorta has a 4-1-2 ratio.

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